Many, if not most, computer systems provide for linking a host computer operating system to one or more peripheral devices which are used as data storage media. For example, the AIX and OS/2 operating systems made by International Business Machines Corporation of Armonk, N.Y. can interface with several different types of data storage peripheral devices that have a so-called Small Computer System Interface (SCSI) interface format.
Included among SCSI devices are magnetic tape data storage devices, magnetic disk data storage devices, and optical disk data storage devices. Also included among SCSI devices are medium changer library devices, each of which contains several data storage devices. In medium changer devices, one of the data storage disks at a time can be selected and then engaged with a transport element within the device for accessing data of a storage device.
Indeed, a multiplicity of data storage devices are made by various manufacturers, each of which may transfer data in accordance with its own unique operating command sequence. It is nonetheless desirable that a host operating system be capable of communicating with as many different types of data storage devices as possible, so as not to unduly restrict the ability of the operating system to interact with available data storage devices.
Accordingly, to permit the host operating system to communicate with several different types of data storage devices, the host operating system ordinarily includes software modules referred to as device drivers. For each data storage device sought to be used by the host operating system, the host operating system must include an associated device driver which is tailored for communicating with the particular device. Thus, each device driver functions as an intermediary between the operating system and the data storage device that is associated with the device driver. More particularly, the device driver receives input/output (I/O) requests from the operating system and then issues commands to its associated data storage device to satisfy the I/O requests.
Many computer systems require device support for a large number of different peripheral devices. Oftentimes, these different devices are typically tape drives, optical devices, magnetic heads, etc. In conventional systems, a device driver must be written for each class of device. In addition, each operating system such as OS/2, UNIX, etc., will require a separate device driver for each operating system. Hence, as is seen, there can be many different device drivers written for each device type or class that is to operate with the computer system as well as for each operating system associated with each device. For example, the ADSM server requires device support for a large number of SCSI peripheral devices on several operating system platforms. Among these platforms are AIX, SUN Solaris and HP/UX. It must be economical to add new devices on all these platforms, and others in the future and it must also be economical to port the entire set of device support to a new operating system platform in the future.
Thus, for each type of data storage device sought to be used by an operating system, the operating system must include an associated device driver. It will be appreciated that each separate operating system must in turn include a plurality of device drivers that are designed for the operating system. Unfortunately, such duplication of system design effort is time-consuming and costly.
For example, it is possible to provide an individual device driver for each class of device and each operating system environment. If there are three device classes and three operating system environments, this means 9 device drivers must be written. As the number of classes and platforms grows, the number of drivers required can become very large.
Accordingly, what is needed is a system for reducing the number of drivers necessary for each operating system. In addition, what is needed is a system or method for reducing the number of device drivers required for each device. In so doing, it is important that the operating system not be substantially modified. The system and method should be one in which there is minimal additional cost to the operating system. The present invention addresses such a need.